1. Field
The present disclosure relates generally to chucks for rotary machine tools, and more particularly, to a quick change jaw system for a chuck.
2. Description of the Related Art
Quick-change jaw assemblies of the type with which the present invention is concerned are typically used in chucks for rotary machine tools. Such a chuck jaw assembly typically includes a radially displaceable master jaw mounted on the chuck body and a top jaw releasably secured to the master jaw to facilitate rapid jaw change. The top jaw provides a clamping or gripping surface adapted to engage a workpiece at either its outside or inside diameter and to hold the workpiece during a machining operation. Normally, the gripping or clamping surfaces on the top jaws are machined after the top jaws have been mounted on the master jaws to assure concentricity of the clamping surfaces relative to the axis of rotation of the chuck.
Chucks having jaws of the aforedescribed quick-change type are particularly well suited for use in repetitive small batch production operations where frequent changeover is required. At the end of each production run, it is usually necessary to remove the top jaws from the chuck and replace them with another set of top jaws particularly adapted to accommodate the next workpiece which may be of a substantially different size or configuration. Desired close workholding tolerances can be maintained by remachining the top jaws after changeover. However, the remachining process is costly and time consuming.
Another approach to the maintenance of precise tolerances after jaw changeover requires that the top jaws and master jaws be marked and maintained as matched pairs for subsequent use. While this practice is advisable with all chucks, this approach introduces the possibility of human error and makes it impossible to interchange top jaws from one chuck to another. If proper matching is not maintained, clamping surface tolerances may be lost and any spindle runout condition which may have existed in the initial jaw setup will be compounded in a subsequent mismatched jaw setup. Additionally, an inventory of required matched pairs can be very costly to maintain.
Heretofore, various jaw assemblies have been available which provide interchangability among top jaws so that the top jaws may be randomly assembled with the master jaws on a chuck without remachining while still maintaining clamping surface tolerances. However, such jaw assemblies generally employ complex mounting mechanisms and are usually costly to produce. Further, such interchangeable jaw assemblies often employ spring biasing mechanisms for urging reference surfaces on the master and top jaws into coengagement and often fail to provide the degree of reliability and chucking tolerances desired.
Therefore, a need exists for an improved interchangeable type quick change jaw assembly of simple, durable construction wherein a single fastener which releasably secures a top jaw to a master jaw also functions to provide a positive sustained biasing force of substantial magnitude for urging reference surfaces on the respective jaws into and maintaining the surfaces in coengagement to assure precise top jaw and master jaw alignment.